1. Field of the Invention
The invention relates to devices for metering a flow rate of gas, such as those know as throttle bodies, for metering combustion air supplied to internal combustion air supplied to internal combustion engines, or alternatively metering bodies, for metering recirculated exhaust gases.
2. Description of the Prior Art
U.S. Pat. No. 4,846,441 discloses a valve, that can be used as a device for metering a fluid flow rate. The valve is of the type comprising a body through which there passes at least one passage in which an approximately disk-shaped throttling member, generally called a butterfly, is mounted to rotate with a shaft transverse to said passage and journal-mounted in the body on each side of the passage. The valve also comprises an end part of which is housed in a chamber formed in the body on one side of said passage and opening laterally to the outside of the body. The end part of the shaft has at least one recess, delimited by a step or a groove, in which recess there is engaged, substantially tangentially to the shaft, at least one tooth which axially locks the shaft in the body, being held in the body by a locking member kept in position in said chamber by means of a plug that closes said chamber.
In U.S. Pat. No. 4,846,441, the shaft is made up of two separate shaft parts, each of which is journal-mounted in a respective one of two lateral bearings of the body and has its external axial end housed in a respective one of two chambers of the body which open laterally to the outside thereof. Each shaft part is fixed to the throttling member of radial screws.
Two teeth, which are cylindrical rods, are introduced independently of one another and tangentially into the annular groove of at least one of the shaft parts and into straight transverse and parallel housings in the locking member. The locking member is a sleeve surrounding the end of the shaft part that has the groove. The sleeve is engaged in the corresponding lateral chamber of the body, so as to retain the cylindrical rods that axially lock the shaft part. In this chamber of the body, the axial positioning of the sleeve is provided by screwing or unscrewing a threaded plug. The screw is screwed into this chamber, without coming into axial abutment against the body, so as to adjust the axial position of the shaft within the body and the position of the throttling member in the passage, to allow it to rotate therein.
Assembling the valve and axially adjusting the shaft parts and the throttling member are lengthy and complicated. Each shaft part which has a groove is introduce into the corresponding sleeve. Then the cylindrical rods that form teeth for axially locking the corresponding shaft part are mounted in the groove and in the sleeve. The subassembly obtained is then mounted in its bearing in the body and connected to this body by screwing the threaded plug. Each shaft part is then fixed to the throttling member by screwing. Finally, the throttling member is centered with respect to the passage of the body by rotating the threaded plug, then immobilizing this plug in position with respect to the body when the desired axial position has been obtained.
The drawbacks of such a device are that it is of a structure, assembly and adjustment that are complicated and expensive and imply accessibility that cannot be given to throttle bodies or metering bodies for metering the flow rate of gases such as combustion air or recirculated exhaust gases.
The problem underlying the invention is that of overcoming the drawbacks of the know devices of the aforementioned type, and of proposing an improved device which is better suited than the know devices to the various requirements of real life. Particularly in the applications to the metering of flow of combustion air supplying an internal combustion engine or to the metering of recirculated exhaust gases.